The present invention relates generally to welding and, more particularly, to a method and system of dynamically controlling operation of a plurality of metal inert gas (MIG) welders to perform a cooperative welding process. By dynamically controlling operation of the plurality of MIG welders between subordinate and superior operational states, a cooperative welding process is achieved across variations in welding parameters.
MIG welding, also known as Gas Metal Arc Welding (GMAW), is a process where an electrical arc is created between a continuous, consumable wire electrode and a workpiece. A wire feeder is typically used to deliver the consumable wire to the weld. The wire feeder is generally connected to a power source that powers the driver motor(s) of the wire feeder as well as delivers welding power to generate a welding arc. As such, the consumable wire functions as the electrode in the weld circuit as well as the source of filler metal.
Some applications require that particularly thick workpieces or heavy welds be utilized. Accordingly, some MIG welding systems have been designed to provide increased weld deposition at reduced per welder currents in order to produce a more uniform distribution of heat in the weld pool. This often results in an improved weld having fewer defects when welding heavy materials. In particular, welding systems have been developed that include two MIG welders that operate together to carry out a “tandem” or “twin” welding process. That is, two MIG welders are used to conjunctively weld a single workpiece.
To create these “dual”, “tandem”, or “twin” systems, two separate MIG welders are combined to create an overall system having two power sources, two wire feeders, and two welding torches. To perform the desired welding process, both welding torches are positioned near the workpiece such that two independent welds are performed on the workpiece. However, if the welding torches of both MIG welders are positioned in close proximity, the arcs from both torches may undesirably interact. Such interaction is undesirable because it negatively affects the consistency and control of the welding process. For example, if the two welding arcs have different polarities, the magnetic fields generated by the arcs push the arcs away from one another. On the other hand, if the arcs have the same polarity, the magnetic fields induced by the arcs oppose one another and push the arcs inward.
As such, traditional dual welding systems include sufficient separation of the welding torches so as to substantially reduce the potential of arc interaction. However, by separating the welding torches, the weld pool is given an opportunity to at least partially solidify after the first welding torch passes and before the second welding torch arrives. In this case, rather than compounding the welding procedure to achieve the desired increased penetration and deposition at the weld, the second welding torch “re-welds” the weld formed by the first welding torch. That is, the first welding torch performs the weld, the weld then solidifies following the departure of the first welding torch, and then the second welding torch arrives at the weld to perform a “re-weld.”
To overcome these problems, some welding systems have been designed that operate according to a “switched” MIG welding procedure. In particular, in order to make operating two-arcs in close proximity feasible, some systems have been designed to switch or alternate the application of the first arc and the second arc to the weld. To achieve the switching of each arc current, various systems have been utilized to limited success.
One switching MIG welding system dedicates one power source to simultaneously supplying a low current to both welding torches while the other power source switches a supply of high current between the two welding torches. As such, these switching MIG welding systems employ a commutator that switches the high current supply from one power source between the two electrodes while the second power source supplies a low current supply to sustain the arc as the high current is switched.
However, these systems must include a specialized power source that includes the switching circuitry necessary to switch the high current supply between the welding torches. As such, the output of the welders may not be independently controlled. Therefore, the welding parameters, such as the wire feed speeds, phase frequencies, wire diameters, and wire types must be the same for both welding outputs, which hinders flexibility in tailoring the welding procedure to a particular application. That is, it may be desirable to augment several variables of a MIG welding process to meet the needs of the specific welding procedure to be performed. For example, MIG welding may be used to weld most commercial metals and alloys including steel, aluminum, and stainless steel. As such, it may be desirable to vary the wire feed speed and the deposition rates between the two MIG welders. However, such variances are not generally possible in these switching MIG welding systems. Furthermore, since both power sources must be adapted to be dedicated to the specialized dual welding procedure, these switching systems do not include two independent MIG welders that may readily operate independent of the dual arrangement. Additionally, these switching MIG welding systems cannot typically be expanded to include more than two welders.
Another switching MIG welding system utilizes two welders arranged in a master and slave configuration. In this case, a master power source is designated to control the operation of the other power source, which is designated as a slave power source. With such an arrangement, the master power source tells the slave power source when to apply high currents to the weld. As such, the master power source, directly or indirectly, controls the timing of the application of high current supplied to both welding torches. In particular, the master power source includes an oscillator whose output is directly supplied to a pulse generator connected to create a high current pulse at the master welding torch. In addition to its direct connection to the pulse generator of the master power source, the output of the oscillator is sent from the master power source to the slave power source. At the slave power source, the signal from the oscillator is subjected to a delay circuit before it is delivered to a pulse generator of the slave power source. Accordingly, the slave power source is not caused to deliver a high current to the slave welding torch until the expiration of a predetermined or user-selected delay. In this regard, the high current pulses supplied to the master welding torch and the slave welding torch are staggered so as to not interact.
While the master/slave MIG welding system achieves a staggered output to reduce arc interaction, by employing a static delay, the master/slave MIG welding system cannot adapt to varying welding parameters between the master welder and the slave welder. That is, welding parameters such as the wire feed speed, phase frequency, wire diameter, and wire type must be consistent between the master and the slave welder. Accordingly, master/slave systems lack the flexibility necessary to tailor the dual welder procedure to a particular application. Furthermore, such MIG welding systems are generally not expandable to include more than a single master welder and a single slave welder.
Therefore, these conventional “tandem” systems are limited to only two welders. That is, both the switching power source dual welder configurations and the master/slave configurations are not designed to incorporate more than two welders. As such, these systems are often referred to as “tandem” welding systems.
It would therefore be desirable to have a system and method capable of performing a multi-welder MIG welding process based on a dynamically controlled pulse welding procedure to accommodate varying welding parameters between the multiple MIG welders. Furthermore, it would be desirable that the multi-welder MIG welding system that can include more than two independent MIG welders. Additionally, it would be desirable to have a welder capable of operating as a stand-alone welder or as part of a multi-welder system.